Made use of `esxml-head'

Changed esxml to make use of tali's new `esxml-head' function.  Also
refactored `(file-name-sans-extension (file-name-nondirectory
wikipage))' into a separate function.
Minor tidying.

Removed extra variable `page-info' in a let binding, and just rebind
`pageinfo'.
Licensing change

Replaced Emacs logo (emacs.png) with Nic Ferrier's cloud gnus image
because I couldn't find any licensing information on the Emacs logo.

Relicensed Elwiki under the AGPL, updating the copyright notices
accordingly.

There is now a COPYING file stating the licensing of Elwiki, Nic's
image, and the example creole page.